In array substrates used in flat display devices such as liquid crystal display (LCD) devices and organic light-emitting diode (OLED) display devices, gate lines are often controlled by a gate driver on array (GOA). The GOA often includes a plurality of cascading shift registers, which are controlled through one or more clock signals, e.g., pulse signals. However, in conventional technology, it is difficult to flexibly adjust the pulse width of the triggering signal for a shift register. As the driving flexibility of gate drivers becomes more desired, conventional shift registers need to be improved.